Analog input digital boundary scan cell, comparator, and analog switches

Abstract

The disclosure describes a novel method and apparatus for improving interposers that connected stacked die assemblies to system substrates. The improvement includes the addition of IEEE 1149.1 circuitry within interposers to allow simplifying interconnect testing of digital and analog signal connections between the interposer and system substrate it is attached too. The improvement also includes the additional 1149.1 controlled circuitry that allows real time monitoring of voltage supply and ground buses in the interposer. The improvement also includes the additional of 1149.1 controlled circuitry that allows real time monitoring of functional digital and analog input and output signals in the interposer. The improvement also provides the ability to selectively serially link the 1149.1 circuitry in the interposer with 1149.1 circuitry in the die of the stack.

What is claimed is: 
     
       1. An analog input boundary scan cell comprising:
 (a) a digital scan cell having a test data input (TDI), a test data output (TDO), a compare input, a first switch output, and a control input; 
 (b) a comparator having a voltage reference input, a functional input and a compare output coupled to the compare input; 
 (c) a first analog switch having a control input coupled to the first switch output, a first voltage input at a first voltage, a second voltage input at a second voltage different than the first voltage, and a first switch output; and 
 (d) a second analog switch having a functional input coupled to the functional input of the comparator, a first switch input coupled to the first switch output, a mode input, and a second switch output. 
 
     
     
       2. The analog input boundary scan cell of  claim 1  in which the digital scan cell includes a capture, shift update (CSU) scan cell. 
     
     
       3. The analog input boundary scan cell of  claim 1  including a unity gain voltage follower amplifier having an input coupled to the second switch output. 
     
     
       4. The analog input boundary scan cell of  claim 1  in which the comparator functional input receives a time varying analog signal. 
     
     
       5. The analog input boundary scan cell of  claim 1  in which the first voltage is voltage level high and the second voltage is voltage level low. 
     
     
       6. The analog input boundary scan cell of  claim 1  in which the first switch output controls switching the first switch output between the first voltage and the second voltage. 
     
     
       7. The analog input boundary scan cell of  claim 1  in which the mode input controls switching the second switch output between the first switch output and the functional input. 
     
     
       8. An analog input boundary scan cell comprising:
 (a) a functional input; 
 (b) a functional output selectively coupled to the functional input; 
 (c) a voltage reference input; 
 (d) a test data input; 
 (e) a test data output coupled to the test data input, the functional input, and the voltage reference input; 
 (f) a control input selectively coupling the test data input to the test data output and selectively coupling a combination of the functional input and the voltage reference input to the test data output; 
 (g) a first voltage input at a first voltage selectively coupled to the functional output; 
 (h) a second voltage input at a second voltage different than the first voltage selectively coupled to the functional output; and 
 (i) a mode input selectively coupling the functional input to the functional output and selectively coupling one of the first voltage input and the second voltage input to the functional output. 
 
     
     
       9. The analog input boundary scan cell of  claim 8  including a digital scan cell having an input coupled to the functional input. 
     
     
       10. The analog input boundary scan cell of  claim 8  including a digital scan cell having an output coupled to the functional output. 
     
     
       11. The analog input boundary scan cell of  claim 8  including a digital scan cell and a switch coupling the first and second voltage inputs to the functional output. 
     
     
       12. The analog input boundary scan cell of  claim 8  in which the digital scan cell is coupled to the test data input, the test data input, and the control input.